1. Field of the Invention
The present invention relates to document processing equipment which executes erasing of one character line en bloc and line by line, the said character line being printed on a sheet of paper and composed of the enlarged characters covering several lines.
2. Related Background Art
The printing systems presently employed for document processing such as electronic typewriter are divided into two types, one being an impact system wherein daisy wheel etc. is struck by a hammer to transfer the ink from the ribbon coated with an ink to a sheet of paper and the thermal transcription system wherein thermal head etc. is heated so that ink is transferred from the ribbon coated with an ink to a sheet by heat. When printing is executed with such document processing equipment for the printing of enlarged characters such as characters, enlarged 4 times by using double character width and double character height or characters enlarged 9 times by using triple character width and triple character height, one character is divided to cover a plural number of lines, such as two or three lines depending on the width of ink ribbon and it is printed by shifting the sheet in the longitudinal direction of the sheet. Likewise, to erase an enlarged character, erasing is done over a plural number of lines by shifting the sheet in longitudinal direction of the sheet. On the other hand, erasing en bloc of a character line printed on a sheet is executed by specifying the scope of words in the document memory and erasing the characters contained in such scope as for every character unit. FIG. 2 is the model drawing to explain the order of steps of erasing en bloc a word composed of characters enlarged by 4 times. FIG. 2A is an example of performance of erasing en bloc of a character line by conventional method wherein steps .circle.1 to .circle.6 are executed by this order. In the Figure, step .circle.1 is erasing of lower half of A, .circle.2 --upper half of A, .circle.3 --lower half of B, .circle.4 --upper half of B, .circle.5 --lower half of C and .circle.6 --upper half of C. At this time, at the change-over of action at the end of each step, namely, at the change-over from .circle.1 to .circle.2 , .circle.2 to .circle.3 , .circle.3 to .circle.4 , .circle.4 to .circle.5 , .circle.5 to .circle.6 and at the end of .circle.6 , the sheet is shifted in the longitudinal direction. However, in the aforesaid example, when the characters composing the character line are enlarged characters, the sheet is shifted in longitudinal direction at each performance of erasing of one character and it brings about the following problems:
(1) Processing speed is slow. PA1 (2) Accuracy of erasing is low. PA1 (3) Power consumption is large.